This invention relates to rotary actuators for producing an output power by converting the reciprocatory linear movement of a piston caused by a fluid pressure into the reciprocatory rotary movement of an output shaft, and more particularly it is concerned with an actuator of the type described that can be utilized as an oscillating actuator for automatically opening and closing various types of valves and for operating a 90.degree. rotary mechanism.
Rotary actuators of the aforesaid type are known.
In one type of rotary actuator of the prior art, a cylinder section formed at opposite ends with a fluid inlet port and a fluid outlet port and formed for containing a reciprocatory piston therein, and an output shaft section containing an output shaft coupled to the piston for rotation are constructed as a unitary structure. An electromagnetic valve for operation and a pressure reducing valve, etc., are connected through pipes to the inlet and outlet ports of the cylinder section to operate the rotary actuator.
In this type of rotary actuator of the prior art, it has hitherto been necessary to separately support an instrument or machine which is connected to an output shaft in the output shaft section. Because of this, when a positioner is assembled with the rotary actuator for controlling the position to which the output shaft of the rotary actuator rotates or when a switch actuated by the rotation of the output shaft of the rotary actuator, such as a limit switch, is assembled with the rotary actuator, it has hitherto been necessary to provide means for stationarily retaining a casing for the positioner or limit switch separately from the rotary actuator. Thus, the problems encountered in this type of rotary actuator of the prior art are that an additional space is required for the retaining means, that it costs an additional workforce for mounting the retaining means and that costs are increased as a result.